1. Technical Field of the Invention
The present invention relates to a plasma processing apparatus utilizing a microwave.
2. Description of the Related Art
Conventionally, there is known a plasma processing apparatus which includes an antenna consisting of a waveguide arranged on the upper of a processing container to supply its interior with a microwave, as shown in FIG. 7.
This plasma apparatus 11 has a processing container 13 on which an antenna 15 is mounted. The antenna is formed by an annularly-curled waveguide having its closed end and has slots 17 formed on the side of the processing container 13. The other end of the antenna 15 is connected to a microwave generator.
In the plasma processing apparatus 11, the microwave from the generator 19 is reflected on the end 21 of the antenna 15 to form a standing wave in the waveguide. Then, the microwave is emitted into the processing container 13 through the slots 17 . . . thereby to generate a plasma for processing.
FIG. 8 shows another plasma processing apparatus 31 in which an antenna 35 in the form of an annular waveguide is wound round the outer periphery of a processing container 33 and also connected to a microwave generator 35 through a waveguide 37. In operation, the microwave supplied from the generator 39 is divided into left and right at a connecting part between the waveguide 37 and the antenna 35. Then, the so-divided microwave meet again at a part 43 on the opposite side of the connecting part 41 and is reflected mutually to form a standing wave in the antenna 35. Through slots 45 formed on the inner side of the antenna 35, the microwave is emitted into the processing chamber 33 subsequently to the above reflection, so that the plasma is produced in the container 33 for processing.
In the above-mentioned plasma processing apparatuses 11 and 31 each forming the standing wave in the antenna, however, the microwave has different intensities at each node and antinode of the standing wave. Thus, due to the positional relationship between node and antinode in the antenna, the interior of the processing container has an electromagnetic field of uneven intensity. Consequently, since the plasma produced in the processing container has an unevenness in its density, the existing plasma processing system has a problem of impossibility to maintain the uniformity of processing, hitherto.
In order to solve the above-mentioned problem, the object of the present invention resides in the provision of a plasma processing apparatus which is capable of producing an uniform plasma in a processing container thereby to accomplish an uniform processing.
The first feature of the invention resides in the plasma processing apparatus comprising: a processing container in form of a cylinder with a bottom; a supporting unit disposed in the processing container to support an object to be processed; a dielectric window arranged so as to oppose the object supported by the supporting unit to close up an opening of the processing container; an annular waveguide shaped to be an endless ring and also fitted to the dielectric window to introduce a microwave into the processing container through the dielectric window, the annular waveguide having a dielectric window part arranged along the dielectric window; a propagation waveguide connected to the annular waveguide to supply the microwave to the annular waveguide; and a microwave supplier connected to the propagation waveguide to supply the microwave to the propagation waveguide, wherein the annular waveguide is arranged so that an antinode of a standing wave of the microwave in the waveguide is located at the dielectric window part.
The second feature of the invention resides in that the microwave supplier is constructed so as to supply a high-frequency wave having a half wavelength longer than the length of the object.
The third feature of the invention resides in that the annular waveguide is shaped to be generally rectangular.
The fourth feature of the invention resides in that the annular waveguide is generally D-shape having a circumferential part and a straight part connected with the circumferential part, the straight part being arranged along the dielectric window.
The fifth feature of the invention resides in that the annular waveguide is shaped spirally and a side face of the spirally-shaped waveguide is arranged along the dielectric window.
The sixth feature of the invention resides in the plasma processing apparatus comprising: a processing container in form of a cylinder with a bottom; a supporting unit disposed in the processing container to support an object to be processed; a dielectric window arranged so as to oppose the object supported by the supporting unit to close up an opening of the processing container; an annular waveguide shaped to be an endless ring and also fitted to the dielectric window to introduce a microwave into the processing container through the dielectric window, the annular waveguide having its part arranged along the dielectric window; a propagation waveguide connected to the annular waveguide to supply the microwave to the annular waveguide; and a microwave supplier connected to the propagation waveguide to supply the microwave to the propagation waveguide, wherein a traveling wave is generated in the annular waveguide by the microwave supplied from the propagation waveguide.
The seventh feature of the invention resides in that the annular waveguide is shaped to be generally rectangular.
The eighth feature of the invention resides in that the annular waveguide is generally D-shape having a circumferential part and a straight part connected with the circumferential part, the straight part being arranged along the dielectric window.
The ninth feature of the invention resides in that the annular waveguide is shaped spirally and a side face of the spirally-shaped waveguide is arranged along the dielectric window.
The tenth feature of the invention resides in the plasma processing apparatus comprising: a processing container in form of a cylinder with a bottom; a supporting unit disposed in the processing container to support an object to be processed; a dielectric window arranged so as to oppose the object supported by the supporting unit to close up an opening of the processing container; an annular waveguide shaped to be an endless ring and also fitted to the dielectric window to introduce a microwave into the processing container through the dielectric window, the annular waveguide having its part arranged along the dielectric window; a propagation waveguide connected to the annular waveguide to supply the microwave to the annular waveguide; a microwave supplier connected to the propagation waveguide to supply the microwave to the propagation waveguide; and a traveling-wave supplier for supplying the microwave which has been propagated through the propagation waveguide, into the annular waveguide as traveling wave.
The eleventh feature of the invention resides in that the traveling-wave supplier is a directional coupler.
The twelveth feature of the invention resides in that the annular waveguide is shaped to be generally rectangular.
The 13th feature of the invention resides in that the annular waveguide is generally D-shape having a circumferential part and a straight part connected with the circumferential part, the straight part being arranged along the dielectric window.
The 14th feature of the invention resides in that the annular waveguide is shaped spirally and a side face of the spirally-shaped waveguide is arranged along the dielectric window.
The above and other features and advantages of this invention will become apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing preferred embodiments of the invention.